Ignition safety switch



Feb. 6, 1968 H. ZWEBEN IGNITION SAFETY SWITCH Filed Jan. '7, 1966 M r M. V M

,arra ZA/E'y United States Patent 3,367,439 IGNITION SAFETY SWITCH Harold Zweben, Plainview, N.Y., assignor to Francis A. Fischel, New York, and Daniel Mantel, Lindenhurst, N.Y.

Filed Jan. 7, 1966, Ser. No. 519,232 8 Claims. (Cl. 180104) ABSTRACT OF THE DISCLOSURE A short circuiting switch for an internal combustion engine in which the shorting electrodes are carried in a cavity and separated by an insulating oil, changing the proper operating orientation of the engine brings a conducting liquid also carried in the cavity below the oil, into contact with the electrodes thereby short circuiting the engine ignition.

This invention relates to an ignition switch for shortcircuiting the high voltage line connected to a distributor or to a spark plug when an internal combustion engine is tilted away from its normal operating position. The invention has particular reference to a switch for a power lawn mower which may be turned on its side or completely turned over.

Power lawn mowers, snow blowers, and other small devices which are powered by internal combustion engines often represent a real hazard when they are tilted out of their normal operating positions and thereby eX- pose rotating blades or other parts of rotating devices which may cause considerable damage when brought in contact with the human body or any other external structure. The need for stopping such devices when they are not in their normal position has been recognized for some time and several cut-out devices have been designed and used for opening the low voltage circuit which supplies the energy for the high voltage spark. All these prior art devices operate in the primary side of the ignition circuit and always act to open a switching means which is normally closed. The present invention operates on the high tension side of the ignition system and is normally open. When the engine is tilted beyond a predetermined normal position, the switch closes thereby short circuiting the high voltage line.

As used throughout the specification and claims, the term high voltage refers to the voltage which is applied to the spark plugs either directly or through a rotating distributor.

An object of the present invention is to provide an improved ignition switch which avoids one or more of the disadvantages and limitations of prior art arrangements.

Another object of the present invention is to short circuit the high voltage line of an internal combustion engine when the engine or its frame has been tilted away from its normal operating position.

A further object of the present invention is to stop an internal combustion engine quickly in order to eliminate dangerous or hazardous conditions caused by uncovering the cutting elements turned by the engine.

Another object of the present invention is to provide a control unit having a conductive liquid which is sensitive to the angular position of its housing.

A still further object of the present invention is to provide a control unit that is inexpensive to manufacture and easy to install.

The invention comprises a nonconducting housing which encloses the switch elements in a hollow space. A first lead-in conductor is sealed in the housing wall and terminated by an upper electrode. A second lead-in conductor is also sealed in the housing wall and is terminated 3,367,439 Patented Feb. 6, 1968 ice by a lower electrode. The space between the two electrodes is filled by a nonconducting oil and a conducting liquid, the conducting liquid normally being in a central receptacle in the lower electrode but adapted to connect the upper and lower electrodes when the housing is tilted. The housing is secured to a portion of the engine so that when the engine is tilted, the housing is tilted an equal amount. The two lead-in conductors are connected across the high voltage circuit of the engine.

One of the features of the present invention is the use of a nonconducting oil which provides the insulation between the two elec'trodes and acts to suppress a spark between the two electrodes when the engine is in its normal position.

The invention consists of the construction, combination and arrangement of parts, as herein illustrated, described and claimed. i

In the accompanying drawing, forming a part hereof is illustrated one form of embodiment of the invention, in which drawing similar reference characters designate corresponding parts in which:

FIGURE 1 is a side view of the switch showing how it is connected to a spark plug.

FIGURE 2 is a cross-sectional view of the switch showing the positions of the electrodes and the receptacle which holds the conducting liquid.

FIGURE 3 is a view similar to FIGURE 2 but shows the switch in a tilted position and the conducting liquid connecting the two electrodes. I

FIGURE 4 is a view similar to FIGURE 2 but shows the switch in an inverted position.

Referring now to the drawing, FIGURE 1 shows the switch 10 secured to a bracket 11 by a bolt 12 and a nut 13a. The bracket is connected to a portion of the engine 13 by means of a bolt 14. The wire 15 is connected to the high voltage end 17 of the spark plug and the lower threaded portion 18 of the spark plug is in contact with the engine body which is grounded. Another high tension wire 20 is connected to that portion of the circuit which generates the high voltage. If there are several spark plugs a distributor is used and conductor 15 is then connected to the central distributor post.

Referring now to FIGURE 2, the switch 10 includes a nonconductive housing 21 having a first lead-in conductor 22 sealed in the upper portion of the housing. This conductor 22 is terminated by an upper electrode 23. Electrode 23 has a lower surface 24 which is in the shape of a cone. The bolt 12 acts as a second lead-in conductor which is also sealed in the housing and is terminated by a lower electrode 25. The lower electrode is formed with a central receptacle 26 and an outer annular inclined surface 27. The two electrodes 23 and 25 are spaced apart from each other and the space between electrodes is filled with a small amount of conducting liquid 28 and a nonconducting oil 30. For most applications it is preferable to have a receptacle 26 large enough to contain all the conducting liquid 28 as shown in FIGURE 2. Also, it is convenient to use the bolt 12, and nut 13, as an electrical connecting means to connect the second lead-in conductor to a portion of the engine block and the other side of the high tension circuit.

FIGURE 3 shows the switch housing in a tilted position with the conducting liquid 28, which may be mercury drained out of the receptacle 26 and moved into the space between the two electrodes, thereby electrically connecting them together and also connecting the high voltage system to ground. This action stops the engine. When the housing is in its normal upright position, the full voltage applied to the spark plugs is also applied to the upper and lower electrodes. Since there is a tendency to spark across the space between electrodes, a nonconducting oil 28 is placed above the conducting liquid and generally fills most of the remaining space. The oil prevents a short-circuiting spark when the housing is upright but does not prevent electrical connection between the two electrodes when the housing is tilted.

FIGURE 4 shows the switch turned upside-down with the conducting liquid forming a ring around the normally upper electrodes and connecting the two electrodes with each other. From these FIGURES 3 and 4, it is obvious that the high voltage circuit is short circuited at any position other than the upright position.

From the above description it is obvious that the invention is a safeguard against any danger which may result from accidental starting when a lawn mower is turned over for repair or cleaning or otherwise inadvertently tipped.

Having thus fully described the invention, what is claimed as new and desired to be secured by Letters Patent of the United States, is:

1. A normally open short circuiting switch for the high voltage circuit of an internal combustion engine comprising a frame on said engine, a non-conducting housing for enclosing the switch elements in a hollow enclosure secured to said frame, a first lead-in conductor sealed in the housing wall and terminated by an upper electrode, a second lead-in conductor also sealed in the housing wall and terminated by a lower electrode, a nonconducting oil and a conducting liquid in the space between the upper and lower electrodes, said non-conducting oil lying between the electrodes when the engine is in operative orientation said conducting liquid normally in contact with the lower electrode but adapted to connect the upper and lower electrodes when the housing is tilted, said housing secured to a portion of the engine so that the housing is tilted when the engine is tilted, said leadin conductors connected across the high voltage circuit of the engine so that the high voltage circuit is short circuited when the upper and lower electrodes are connected.

2. A switch as claimed in claim 1, wherein said conducting liquid is mercury.

3. A switch as claimed in claim 1, wherein a cup-like receptacle is formed in the lower electrode for normally holding the conducting liquid.

4. A switch as claimed in claim 1, wherein said first lead-in conductor is connected to a distributor which switches the high voltage to a plurality of spark plugs, and the second lead-in conductor is connected to a portion of the engine frame.

5. A switch as claimed in claim 1, wherein said first lead-in conductor is connected to a spark plug and the second lead-in conductor is connected to a portion of the engine frame.

6. A switch as claimed in claim 1, wherein said second lead-in conductor is a bolt and adapted to be secured to a conducting portion of the engine.

7. A switch as claimed in claim 3, wherein said receptacle is in the center of the lower electrode and wherein the rim of the receptacle is bordered by an annular inclined surface whereby the conducting liquid flows into the receptacle when the housing is returned to its normal upright position.

8. A switch as claimed in claim 7, wherein said conducting liquid has a higher density than the non-conductive oil.

References Cited UNITED STATES PATENTS 1,588,459 6/1926 Kilgour 20061.47

1,688,217 10/1928 Whalen 200-152 1,228,817 1/1941 Dunn ZOO-61.47

2,456,799 12/1948 Smies 180-104 2,535,207 12/1950 Hook et al.- ZOO-61.47

3,156,795 11/1964 Bonfiglio 20061.52

KENNETH H. BETTS, Primary Examiner. 

